Matching a speaker cabinet to my amplifier...

[metaldome]

I recently bought a Randall RG100ES solid state amplifier and had some questions about pairing it with a speaker cabinet. The manual states "Less than 8 OHM load impedance not recommended," and each output on the back is labeled 8 ohms. However, it also states Power Output 120 watts RMS @ 4 ohms, 80 watts RMS @ 8 ohms. I am thinking they meant not less than 8 ohms into each of the outputs at the same time but this confused me a bit, so I would appreciate it if someone could clarify by answering the following questions...

Would it be alright to connect one 4 ohm or two 8 ohm cabinets?
This would give me 120 watts of power, correct?

Would it be alright to connect one 8 ohm or two 16 ohm cabinets?
This would give me 80 watts of power, correct?

Would it be alright to connect one 16 ohm cabinet?
How many watts of power would this give me?

I should not hook up one 2 ohm or two 4 ohm cabinets, correct?

Thanks for any help!!!

 

[Ayrton]

Re: Matching a speaker cabinet to my amplifier...

You are over thinking this (yes there is more later, but the basics now)

I assume you don't have a cabinet yet, so here are your basic choices.

1x12 with either a 16 or 8-ohm speaker.

2x12 with either two 8-ohm speakers wired in series giving you a 16-ohm load. OR two 16 ohm speakers wired in parallel giving you a 8-ohm load.

4x12 in the same configuration as the 2x12

Your speaker will need to be all the same ohm rating.

 

[Dave Locher]

Re: Matching a speaker cabinet to my amplifier...

I have using a 2x12 cabinet with two 8-ohm speakers wired in parallel for a 4-ohm load with my RG100ES since 1988. Until 2000 I was rehearsing at band volume or playing live most days of the week. So 12 years of heavy use. Absolutely no problems at all.
As best I can tell, anything between 4 and 16 ohms total load works just fine.

 

[Jacew]

Re: Matching a speaker cabinet to my amplifier...

Would it be alright to connect one 4 ohm or two 8 ohm cabinets?
This would give me 120 watts of power, correct?

Is the amp specced as 120w or 80w generally. Because if it is, it seems obvious it can run 4 ohm load, which make the statement about less than 8 ohms very weird.

If 80 watts is enough power you need I'd trust the manual and wouldn't use lower impedance. Though I suspect it would work fine.

Would it be alright to connect one 8 ohm or two 16 ohm cabinets?
This would give me 80 watts of power, correct?

Of course. Yes.

Would it be alright to connect one 16 ohm cabinet?
How many watts of power would this give me?

Yes. 40 watts.

I should not hook up one 2 ohm or two 4 ohm cabinets, correct?

Correct.

 

[Dave Locher]

Re: Matching a speaker cabinet to my amplifier...

They say "120 watts @ 4 ohms" on the back. The original 4x12 cabinets are 8-ohms each, which means if you run it as a full stack it is running at 4 ohms (two 8-ohm cabinets = 4 ohms).

When I switched from the 8-ohm 4x12 to my 4-ohm 2x12 I did not notice any increase in volume. It actually seemed a bit quieter to me, at least in the low end, which I attributed to going from 4 speakers down to 2.
For about a week last winter I was running mine into one 8-ohm Eminence Tonker. Then I added another, dropping the cabinet back down to 4 ohms. Again, no big difference in volume. Just for the heck of it I wired them in series for a couple days. It sounded different, but not way more quiet.
Like I said above, the head does not seem to care if it pushing 4 ohms, 8 ohms, or 16 ohms.